Hitachi Groupmax Mail SMTP 06-50 through 06-52-/A and 07-00 through 07-20 allows remote attackers to cause a denial of service (service stop) via an e-mail message with an "invalid format."
http://www.vupen.com/english/advisories/2005/2492
http://www.securityfocus.com/bid/15499/
http://www.hitachi-support.com/security_e/vuls_e/HS05-024_e/01-e.html